Amoxicillin Oral Suspension Dosing for Children
The volume of amoxicillin suspension you give depends on the child's weight, age, and infection severity—calculate the total daily dose in mg/kg/day, then divide by the concentration of your suspension (125 mg/5 mL or 250 mg/5 mL) to determine the volume per dose.
Dosing Algorithm
Step 1: Determine the Appropriate Dose (mg/kg/day)
For children ≥3 months old and <40 kg:
Mild to moderate infections (ear/nose/throat, skin, genitourinary):
- 25 mg/kg/day divided every 12 hours, OR
- 20 mg/kg/day divided every 8 hours 1
Severe infections or lower respiratory tract infections:
- 45 mg/kg/day divided every 12 hours, OR
- 40 mg/kg/day divided every 8 hours 1
Pneumococcal pneumonia (high-dose therapy):
- 90 mg/kg/day divided in 2 doses, OR
- 45 mg/kg/day divided in 3 doses 2
For infants <3 months old:
- Maximum 30 mg/kg/day divided every 12 hours 1
- Recent evidence supports twice-daily dosing for first 2 days of life, then three times daily from day 3 onward 3
Step 2: Calculate Volume Based on Suspension Concentration
If using 125 mg/5 mL suspension:
- Each mL contains 25 mg amoxicillin
- Volume (mL) = Dose in mg ÷ 25
If using 250 mg/5 mL suspension:
- Each mL contains 50 mg amoxicillin
- Volume (mL) = Dose in mg ÷ 50
Step 3: Practical Example
For a 15 kg child with pneumonia requiring high-dose therapy:
- Total daily dose: 90 mg/kg/day × 15 kg = 1350 mg/day
- Divided twice daily: 675 mg per dose
- Using 250 mg/5 mL suspension: 675 mg ÷ 50 mg/mL = 13.5 mL per dose, twice daily
- Using 125 mg/5 mL suspension: 675 mg ÷ 25 mg/mL = 27 mL per dose, twice daily
Critical Considerations
Maximum dose caveat: The FDA label states doses should not exceed adult doses 1. However, recent evidence shows larger children systematically receive inadequate dosing when capped at adult maximums, particularly those >60 kg receiving <40 mg/kg/day 4. For infections requiring high-dose therapy (pneumococcal pneumonia), prioritize weight-based dosing over arbitrary adult dose caps to ensure adequate antimicrobial exposure 5.
Resistance considerations: High-dose amoxicillin (80-90 mg/kg/day) is specifically recommended for pneumococcal infections due to increasing intermediate penicillin resistance 2, 5. Standard dosing may be inadequate for resistant strains, particularly when using CLSI breakpoints rather than EUCAST criteria 5.
Duration: Continue treatment for minimum 48-72 hours beyond symptom resolution or bacterial eradication 1. For Streptococcus pyogenes infections, treat for at least 10 days to prevent acute rheumatic fever 1.
Storage after reconstitution: Shake well before each use. Discard unused suspension after 14 days. Refrigeration is preferable but not required 1.
Administration tip: Place suspension directly on child's tongue or mix with formula, milk, fruit juice, water, or cold drinks—administer immediately after mixing 1.